The present invention relates to a new and improved method of, and apparatus for, beading the bodies of metal containers, typically sheet metal containers, especially metal cans.
In German Patent No. 2,124,038 there is disclosed a beading apparatus for the fabrication of circular beads or corrugations. By means of a roll arranged noncoaxially within the unbeaded, smooth container the container body is pressed against a curved counter rail or counter roll and rolled upon such curved counter rail or counter roll. The rolls and the rails, as the case may be, possess mutually interengaging congruent profiles which form the beads or corrugations. For exchanging the workpiece the inner roll travels axially out of the working region (container body) and frees the work station for unloading and renewed reloading.
During the machining or processing of containers with the prior art equipment the rotation of the container is accomplished by the frictional force which is present at the clamping nip between the inner roll and the outer roll. However, the force cannot be maintained constant because of the different thickness of the sheet metal material at the circumference of the container, especially when processing soldered containers having four-fold thickness of the sheet metal at the joint locations. This can produce a sliding friction which, in turn, can lead to scratches at the can lacquer or varnish. Additionally, it is impossible to fabricate other than circular beads.
Also there are known to the art apparatuses, especially for large containers, which possess both circular and non-circular cross-sectional configurations, wherein the container can be brought into the desired shape by elongation thereof through the use of radially expandable inner tools.
In the case of circular containers, especially small containers such as sheet metal cans, especially cans used in the foodstuff industry, which are fabricated in piece numbers of up to several thousand per minute by a single machine, the expanding technique no longer can be economically employed.